Lattice mast having an open framework structure in particular an electricity pylon or telecommunication mast, and method for increasing the stability of lattice masts having an open framework structure

ABSTRACT

The invention relates to a lattice mast ( 1 ) with an open framework structure of angled profiles ( 3 ), in particular an electricity pylon or telecommunications mast, comprising at least one or more cladding profiles (9 a,    9   b ) which extend over at least part of the length of at least one angled profile ( 3 ), wherein at least one cladding profile has a curved incident-flow surface and forms a flow shielding of a wind-exposed edge of the angled profile ( 3 ), wherein the incident-flow surface is at least approximately spherically curved and has a flow resistance coefficient which is less than that of the unshielded angled profile ( 3 ).

FIELD

The invention relates to a lattice mast with an open framework structure of angled profiles, in particular an electricity pylon or telecommunications mast.

The invention moreover relates to a method for increasing the stability of a lattice mast with an open framework structure of angled profiles, in particular of electricity pylons or telecommunications masts.

A lattice mast within the sense of the present invention is understood to include, for example, a mast for receiving overhead electricity transmission lines. A radio mast or antenna mast, or a telecommunications mast, is likewise understood as a lattice mast within the sense of the present invention. Lattice masts with open framework structures can, however, also be lattice masts on bridges or pylons. Lastly, a lattice mast within the sense of the present invention can also be a mast for mounting a wind power generator.

An open framework structure within the sense of the present invention is understood to include a framework structure with struts which are not provided with infilling and which is not permanently inhabited and is not used for residential purposes.

The aerodynamic cladding according to the present invention is provided with angled profiles for open framework structures.

BACKGROUND

Framework structures comprising angled profiles have the advantage that they are particularly light and the individual profile struts can be connected to each other relatively easily, for example by rivets, welds or bolts.

Such lattice masts are usually constructed from a row of structural elements arranged one above the other, wherein each stage forms a framework structure which has three or more trapezoidal framework panels which each consist of corner supports braced to one another. The corner supports are designed as angled profiles, and the struts connecting the latter can likewise be designed partly as angled profiles, and partly also as plate profiles.

The design of such framework structures is generally subordinated to the requirements for the bearing load and for the wind load acting on the construction.

The measurement or dimensioning of the structural elements forming the framework structure is, on the one hand, dependent on the free buckling length of the individual elements and on the tensile or compressive stress prevailing in the latter, and, on the other hand, on the interaction of longitudinal forces and lateral forces which are introduced into the construction, for example, by wind loads.

In order to stabilize lattice constructions or framework structures of this type, numerous bracing systems are known which are optimized with respect to the arrangement of the framework struts and with regard to the total weight of the lattice structure. Such a system is described, for example, in GB 675,859 A.

The optimal design of framework structures for the expected wind load and bearing load relative to the optimal weight generally presents relatively few problems. In the case of existing framework structures, for example in the case of existing lattice masts for overhead electricity transmission lines, it may be necessary from time to time to repair and/or replace parts of the structure. In some circumstances, this requires new stability checks. Existing installations do not meet increased stability requirements in some circumstances, in particular also owing to increased load requirements or owing to a structural weakness which is to be expected after standing for a relatively long period of time.

In such cases, there may be a need for time-consuming tensioning. A crane construction is known from DE 1 509 022 US which is characterized in that it is clad at least in part by flow-promoting rotatably mounted hollow profiles which adjust themselves to the respective direction of the oncoming wind.

The support for an overhead transmission line mast, which has a protective concrete cover in the base region, is know from G 87 00 379.1.

Further prior art is known from the documents JP 2002 276 200 A and CN102155106 A.

SUMMARY

The object of the invention is to provide a lattice mast which has a design which can be produced relatively simply in the course of subsequent upgrading.

The object of the invention is moreover to provide a suitable method for increasing the stability of lattice masts as part of subsequent upgrading.

This object is achieved in particular by the features of claim 1 and by the features of claim 11.

Preferred alternative embodiments of the lattice masts and of the method according to the invention for increasing the stability of lattice masts are apparent from the dependent claims.

According to one aspect of the invention, a lattice mast with an open framework structure of angled profiles is provided, in particular an electricity pylon or telecommunications mast, comprising at least one or more cladding profiles which extend over at least part of the length of at least one angled profile, wherein at least one cladding profile has an incident-flow surface and forms a flow shielding of a wind-exposed edge of the angled profile, wherein the incident-flow surface has a flow resistance coefficient which is less than that of the unshielded angled profile.

The incident-flow surface is preferably at least approximately spherically curved or has a polygonal or facetted contour which is similar to a spherical or elliptical arc contour. “Facetted” within the sense of the invention is understood to mean a polygonal surface which is similar to an arc contour.

An angled profile within the sense of the invention is understood to mean, for example, a T-profile, L-profile, I-profile, Z-profile, U-profile, C-profile or the like.

The invention makes use of the fact that the wind load on a construction is determined from the product of a reference pressure with a flow resistance coefficient and of the exposed surface of the construction. The reference pressure is dependent on the air density and the wind speed. The flow resistance coefficient here describes the characteristic of the wind flow about a structural element of the relevant framework structure, for example about an angled profile. Sharp edges of a profile tend to generate turbulence and are therefore more prone to wind loads than facetted or rounded edges or round or tubular profiles. An octagon has, for example, a flow resistance coefficient of Cw=1.3, compared with a flow resistance coefficient of Cw=2.0 for sharp-edged angled profiles.

If the flow rate of a fluid which initially flows laminarly is increased, the characteristic of the flow changes from laminar to neutral and then to unstable so that the initially orderly flow becomes undulating. As a result, the flow resistance coefficient increases significantly. At sharp profile edges, the flow resistance coefficient Cw (dimensionless) can assume a magnitude of approximately 2.0, whilst for round elements or for example also for spherical elements it is approximately between 0.176 and 0.48, depending on the Reynolds number. In the case of very high Reynolds numbers, the resistance coefficient of a sphere increases, whereas it can assume low values in the case of relatively low Reynolds numbers.

The invention makes use of these fluid mechanical circumstances which are known per se. By providing a correspondingly clad lattice mast, the flow resistance coefficient of at least some of the exposed angled profiles can be reduced significantly, as a result of which the wind load on the construction is likewise significantly reduced. In the most simple case, this can be achieved for example by at least one exposed critical edge of an angled profile being shielded with a cladding profile, wherein the cladding profile has a rounded or curved incident-flow surface. In the case of a lattice mast, it can for example be provided to shield all or some of the corner supports or corner profiles by means of corresponding cladding profiles. These cladding profiles can be fastened, for example only over part of the length of the relevant angled profiles, to the latter, and shield the angled profiles in each case only over part of their length. It is likewise possible within the scope of the invention to correspondingly clad only the node points of the framework.

According to another aspect of the present invention, the cladding profiles can be designed with variable cross-sections along the angled profile to be clad in order thus to prevent the possibility of vortices being induced, or to optimize the aerodynamic damping.

In the case of a lattice mast structure, the relevant cladding profile can be arranged, for example, such that it shields the apex of an angled profile, which forms for example an isosceles triangle in cross-section.

In the case of a lattice mast structure having three or four corner supports, the construction is generally selected such that the corner supports are designed as angled profiles with an essentially isosceles-triangle cross-section, wherein the apexes of the relevant angled profiles point outward. A significant reduction in the wind load is obtained by cladding these apexes.

The curved incident-flow surface of at least one cladding profile is expediently arranged symmetrically with respect to the relevant profile edge.

In particular lightweight plastic, aluminum, or steel profiles come into consideration as cladding profiles and these can be designed as shell-like elements but also as solid profiles.

In a preferred alternative embodiment of the lattice mast according to the invention, it is provided that the at least one cladding profile has a maximum projection area which is no more than 60%, preferably no more than 40%, and more preferably no more than 20% greater than the maximum projection area of the unclad angled profile. It is ensured as a result that the incident-flow surface, which is included in the calculation of the wind load, with respect to the unclad profile is not so great that the advantage of the reduced flow resistance coefficient is completely eradicated as a result.

In, for example, the case of a cladding profile with an approximately arc-shaped incident-flow surface, the diameter of the relevant cladding profile can be at most 20% greater than the diagonal of an angled profile designed as a corner profile.

An approximately spherically curved incident-flow surface within the sense of the present invention is also understood to be an elliptical or parabolic or asymmetrically curved incident-flow surface.

An alternative embodiment of the lattice mast according to the invention is characterized in that the at least one cladding profile forms a structural unit with at least one angled profile.

A structural unit within the sense of the present invention is understood to mean that the cladding profile and the relevant angled profile complement each other to form a load-bearing supporting component.

The at least one cladding profile can, for example, be connected to at least one angled profile by means of one or more types of fastening selected from a group comprising adhesive bonding, riveting, welding, clamping, fastening with Velcro, binding, screwing, stapling, or foaming. Combinations of these types of fastening are also possible. For example, a cladding profile can be adhesively bonded to the relevant angled profile, but at the same time the latter can also additionally be fastened by means of straps, bands or the like which are tensioned around the angled profile and the cladding profile.

In an advantageous embodiment of the invention, it is provided that the at least one cladding profile complements the angled profile to form a closed profile cross-section. It can, for example, be understood that the cladding profile closes or covers only one open side of an angled profile.

Instead of the angled profile being complemented to form a closed profile cross-section, it can also be provided that at least one cladding profile partially or also completely encloses the angled profile and forms a closed or approximately closed profile cross-section. For this purpose, it can for example be provided that the cladding profile comprises multiple elements which are connected to one another via a hinge, for example a film hinge.

It can alternatively be provided that multiple cladding profiles form a closed or approximately closed profile cross-section which at least partially encloses the angled profile. These cladding profiles can, for example, be detachably connected to one another, but alternatively they can be fastened to the angled profile, for example in a partially overlapping manner, by means of clamping elements which grip around the angled profile. In a preferred and advantageous alternative embodiment of the cladding, it is provided that multiple cladding profiles complement one another to form a closed or approximately closed spherical or ellipsoidal cross-section. The profile cross-section formed by one or more cladding profiles can completely enclose the angled profile. This profile cross-section does not have to have a symmetrical design and instead the cladding profiles can also form an asymmetrically ellipsoidal cross-section.

This can be achieved for example by two cladding profiles, which are designed as shell-like profile segments, being provided with different radii of curvature, wherein one cladding profile with a first radius of curvature and a second cladding profile with a second radius of curvature complement each other to form a closed profile cross-section and enclose the angled profile, wherein the first radius of curvature is preferably smaller than the second radius of curvature, and the first radius of curvature surrounds the exposed edge to be shielded of the angled profile.

If the angled profile to be clad is, for example, an angled profile with two profile legs and a vertex, the vertex can be shielded by a first cladding profile with a first small radius of curvature, whereas the open side of the angled profile is shielded by a second cladding profile with a second larger radius. In this way, an incident-flow side is defined by the first angled profile, via which incident-flow side an air flow is led out over the free ends of the legs of the angled profile.

The at least one or more cladding profiles are, as mentioned, designed as shell-like profile segments, or alternatively, in particular when it is intended for the cladding profile or profiles in each case to form a complement to the profile cross-section of the angled profile, they can be also designed as solid profiles.

The shell-like profile segments can be arranged spaced apart from the relevant angled profile; for example, the shell-like profile segments can be mounted via webs at a distance from the angled profile.

In the invention, it is provided that at least one or more cladding profiles are back-foamed, wherein the foam simultaneously provides a means of adhesion with respect to the relevant angled profile.

The at least one or more cladding profiles can also be designed as shell-like profile segments, the free edges of which are extended by fringes, fibers, or perforated profiles. In particular as a result of such a design of profile legs, it is possible to prevent the formation of turbulence at the free ends of the profile legs, as a result of which a relatively favorable aerodynamic effect is also obtained.

According to a further aspect of the invention, a method for increasing the stability of lattice masts with an open framework structure of angled profiles, in particular of electricity pylons or telecommunications masts, using at least one cladding profile is provided, wherein the method comprises the cladding of at least one angled profile with at least one cladding profile which has at least one at least approximately spherically curved or facetted incident-flow surface in such a way that at least one wind-exposed edge of the angled profiles is shielded by the relevant cladding profile, wherein the angled profile is complemented or clad to form an essentially closed or approximately closed, at least partially and at least approximately round or facetted profile cross-section.

The method is preferably characterized by a subsequent upgrading of a lattice mast to form an aerodynamically clad lattice mast with one of the abovedescribed features.

In an advantageous alternative embodiment of the method according to the invention, the cladding profiles, in particular those which are designed as a structural unit with an angled profile, are connected at node points of the framework structure so that they overlap the angled profiles and/or to one another in a force-fitting, interlocking, or bonded manner, for example by adhesive bonding, plugging together, clamping, bolting, or screwing. In this way, the entire supporting function of the original framework structure can be replaced by an exoskeleton made from the cladding profiles.

In such an alternative embodiment of the method, the cladding profiles are preferably connected to one another and/or to the angled profiles only at the node points of the framework structure.

Different alternative embodiments of the aerodynamic cladding of lattice masts were described above, wherein the abovedescribed alternative embodiments of the cladding can be applied in combination on a single lattice mast.

Within the scope of the invention, the aerodynamic cladding of all the profiles and profile struts of the framework structure is possible, wherein, as also indicated above, also only parts of this lattice mast or also only nodes of the framework can be clad correspondingly.

The cladding profiles can be formed both as individual profile shell segments and as individual solid profile elements or from multiple profile segments which are connected inseparably to one another.

The method preferably comprises the fastening of the cladding profiles to the lattice mast with a framework structure with the aid of at least one climbing robot.

DESCRIPTION OF THE DRAWINGS

The invention is explained below with the aid of an exemplary embodiment shown in the drawings, in which:

FIG. 1 shows a schematic view of a lattice mast as an overhead transmission mast for holding overhead electricity transmission lines,

FIG. 2 shows a cross-section through a corner support of the lattice mast shown in FIG. 1, with an aerodynamic cladding according to the invention according to a first alternative embodiment, and

FIG. 3 shows a section through a corner support of the lattice mast shown in FIG. 1, with an aerodynamic cladding according to a second alternative embodiment according to the invention in an exploded view.

DETAILED DESCRIPTION

The lattice mast 1 in FIG. 1 is designed as a conventional open steel framework construction with four corner supports 2 which in the present case are designed as open angled profiles 3 with two legs 4 of equal length and a vertex 10.

As can be seen in FIG. 1, in the region where it is erected the lattice mast occupies a relatively large footprint, and the four corner supports 2 of the lattice mast 1 converge in the direction of the mast tip 5. In each case, two corner supports 2 form, together with cross-struts 6, trapezoidal panels of a mast stage. Each mast stage is overall described by four trapezoidal panels, and multiple mast stages extend vertically from the base of the lattice mast 1 to its mast tip 5. The individual panels of the stages of the lattice mast 1 are designed as framework structures with diagonally extending struts which act as pressure rods or tension rods depending on the magnitude of the transverse loading of the lattice mast 1. The lattice mast 1 owes its shape, which tapers toward the mast tip 5, to the expected bending stress on the lattice mast 1 due to wind load and due to the bearing load of the lines. The lines 7 are suspended from mast cross-arms 8 in a known fashion. The geometry of the mast cross-arms 8 is adapted to the expected bending moment distribution resulting from the weight of the lines 7.

A view in section of a corner support 2 of the lattice mast 1 as an angled profile 3 within the sense of the present application is shown in FIG. 2, which illustrates a first exemplary embodiment according to the invention.

The cross-struts 6 provided on the lattice mast 1, the diagonal struts provided on said cross-struts, and other structural elements can likewise be clad in a corresponding aerodynamic fashion as angled profiles within the sense of the invention.

Two cladding profiles, a first cladding profile 9 a of which is designed as a profile shell segment with a first radius of curvature and a second cladding profile 9 b of which is designed as a second profile shell segment with a second radius of curvature, are fastened at the corner support 2 as aerodynamic cladding.

Both the first cladding profile 9 a and the second cladding profile 9 b can be designed, for example, in the form of plastic shells which can be adhesively bonded, screwed, riveted, stapled, or otherwise connected to the angled profile 3. The first cladding profile 9 a is designed as a curved profile shell with a first smaller radius of curvature, whereas the second cladding profile 9 b is likewise designed as a curved profile shell with a second larger radius of curvature. Both cladding profiles 9 a and 9 b completely enclose the angled profile and form a closed, asymmetrically ellipsoidal cross-section.

The first cladding profile 9 a forms an incident-flow surface which shields and surrounds the vertex 10 of the symmetrically designed angled profile 3. The first cladding profile 9 a is connected to the symmetrical angled profile 3, or fastened to the latter, in the region of the ends of the legs 4 of said symmetrical angled profile 3. The second cladding profile 9 b, which clads and shields that open side of the angled profile 3 which is opposite the vertex 10, has a relatively larger radius of curvature and is likewise fastened to the angled profile 3 in the region of the ends of the legs 4 of the angled profile 3.

In the exemplary embodiment shown in FIG. 2, flow shielding of the vertex 10 is primarily provided, and the first cladding profile 9 a is accordingly arranged symmetrically with respect to the vertex 10 and forms the windward side of the flow profile, whereas the second cladding profile 9 b forms the lee side.

In the drawings, the cladding enclosing as a whole the angled profile 3 is designed as closed, but the invention is to be understood such that the profile surface does not need to be completely closed and instead it can also be designed to be only partially closed on the lee side (second cladding profile 9 b).

As can also be seen in particular in the drawing in FIG. 2, the maximum diameter of the first cladding profile 9 a and hence of the whole clad profile cross-section is greater by a factor of 1.2 than a diagonal which connects the ends of the legs 4 of the angled profile 3. In other words, the projected area of the completely clad angled profile 3 is greater by a factor of 1.2 than the projected area of the unclad angled profile 3.

In the alternative embodiment of the aerodynamic cladding shown in FIG. 3, a first cladding profile 9 a and a second cladding profile 9 b are likewise provided which are each designed as solid profiles which are likewise connected to the legs 4 of the angled profile 3 in a form-fitting or bonded manner. The cladding profiles 9 a, 9 b according to the second exemplary embodiment complement the symmetrical angled profile 3 to form an asymmetrically elliptical profile which is similar to a round cross-section.

LIST OF REFERENCE NUMERALS

1 lattice mast

2 corner supports

3 angled profiles

4 legs

5 mast tip

6 cross-struts

7 lines

8 mast cross-arms

9 a first cladding profile

9 b second cladding profile

10 vertex 

1. A lattice mast with an open framework structure of angled profiles, comprising at least one cladding profile that extends over at least part of the length of at least one angled profile, wherein said at least one cladding profile has an incident-flow surface that forms a flow shielding of a wind-exposed edge of the angled profile, wherein the incident-flow surface has a flow resistance coefficient that is less than that of an unshielded angled profile, and wherein said at least one cladding profile comprises a back-foamed shell-like profile segment.
 2. The lattice mast of claim 1, wherein the incident-flow surface is at least approximately spherically curved or has a polygonal contour which is at least similar to a spherical or elliptical arc contour.
 3. The lattice mast of claim 1, wherein the curved incident-flow surface of the at least one cladding profile is expediently symmetrically with respect to said exposed edge.
 4. The lattice mast of claim 1, wherein said at least one cladding profile has a maximum projection area selected from the group consisting of no more than 60% greater, no more than 40% greater, and no more than 20% greater, than the maximum projection area of the unclad angled profile.
 5. The lattice mast of claim 1, wherein said at least one cladding profile forms a structural unit with at least one angled profile.
 6. The lattice mast of claim 1, wherein said at least one cladding profile is connected to at least one angled profile by at least one fastening selected from a group consisting of adhesive bonding, riveting, clamping, fastening with Velcro, binding, screwing, stapling, and foaming.
 7. The lattice mast claim 1, wherein multiple cladding profiles are connected to one another and/or to at least one angled profile of the framework via nodes of a framework structure, forming a structural unit.
 8. The lattice mast claim 1, wherein at least one cladding profile complements the angled profile to form a closed profile cross-section.
 9. The lattice mast of claim 1, wherein multiple cladding profiles form a closed or approximately closed profile cross-section at least partially enclosing the angled profile.
 10. The lattice mast of claim 1, wherein multiple cladding profiles are complemented to form a closed or approximately closed spherical or elliptical cross-section.
 11. The lattice mast of claim 1, wherein at least one shell-like profile segment comprises profile legs, wherein at least one free end of at least one profile leg is frayed or has strips or holes or at least one additional perforated profile that reduces flow resistance and/or increases aerodynamic damping.
 12. A method for increasing the stability of lattice masts comprising an open framework structure comprising angled profiles, using at least one cladding profile, comprising cladding at least one angled profile with a cladding profile that has at least one at least approximately spherically curved incident-flow surface wherein at least one wind-exposed edge of said angled profiles is thereby shielded by the cladding profile, and wherein the angled profile is complemented or clad at least partially to form an essentially closed or approximately closed, at least partially round or facetted profile cross-section, and further comprising upgrading said lattice mast to form a lattice mast in which the at least one cladding profile is configured as a shell-like profile segment that is back-foamed.
 13. The method of claim 12, further comprising the step of a subsequent upgrading of a lattice mast to form an aerodynamically clad lattice mast as claimed in claim
 1. 14. The method of claim 12, wherein said lattice mast is an electricity pylon or telecommunications mast.
 15. The lattice mast of claim 1, wherein said lattice mast is an electricity pylon or telecommunications mast. 